Furnace for the combustion of solids

ABSTRACT

A shaft furnace equipped with grates, air supply ducts, flues wherein at least one grate forms a fireplace with an air supply duct and the flues.

O Umted States Patent 1191 1111 3,707,931 Ruegsegger 1 Jan. 2, 1973 s41 FURNACE FOR THE COMBUSTION OF 2,284,464 5 1942 Wingert ..110/29 x SOLIDS 2,341,980 2/1944 DBlGll ..1 10 30 2,452,843 1 111948 Egnault-Pelterie ..1 10/29 Inventor: Wllter n Tobelhofstrasse 2,883,947 4/1959 Corey ..110/84 x 348, 8044 Zurich, Switzerland 1,715,954 6/1929 Schuetz ..110/8 2,563,137 8/1951 Sharpe ..110/18 [221 1970 1,311,522 7/1919 1011 ..110/18 3,082,714 3/1963 Close ..110/8 [211 59475 1,787,081 12/1930 McLellan 1.10/18 2,993,454 7/1961 Hebert ..110/8 Morgan x Aug. 18, 1969 Switzerland ..12526/69 FOR IGN PA ENTS 0R APPLICATIONS 876,838 8 1942 F ..llO 29 52 us. 01. ..110/8 0, 110/18 c [51] I111. Cl ..F23g 7/00 primary Examine, ](enneth w Sprague Fleld 0f Search ..1 8 C, 18, C, 29, 30, Anorney B -owdy and Neimark 110/35, 84

[57] ABSTRACT [56] References Cited A shaft furnace equipped with grates, air supply ducts, UNITED STATES PATENTS flues wherein at least one grate forms a fireplace with an air supply duct and the flues. 2,160,481 5/1939 Lockwood ..110/29 1,356,028 10/1920 Waddell, Jr. ..110/30 19 Claims, 6 Drawing Figures FURNACE FOR THE COMBUSTION OF SOLIDS The present invention concerns a furnace for the combustion of solids, in particular a shaft furnace for the combustion of wood waste and refuse, with one or several grates, air supply ducts and flues.

For complete combustion in the chamber of a shaft furnace, wood and refuse require high temperatures for gasification and a long flame path for complete combustion.

However, the flame path from the combustion air supply point to the gas flue must not be too long; if it is too long, too much fuel takes part in the combustion at the same time, or the fire chokes when the combustion air supply is throttled. In the known shaft furnaces, the

flame path increases with increasing shaft size to such adegree that so far it has only been possible to build relatively small shafts. Such small furnaces however, have the drawback that they have to be frequently charged and that the shaft can only take relatively small pieces of refuse.

The object of the present invention is to provide a large shaft-furnace system, permitting even big pieces of refuse and wood waste to be discharged into the shaft directly from the refuse truck. The said object is achieved by providing a system wherein at least one grate forms both functionally and structurally a fireplace in conjunction with the air supply duct or ducts and the flues or the flue hood, the arrangement being such that the combustion air issuing from the grate supplies the fuel in the grate zone with the oxygen necessary for combustion, and that the flue gases mainly stream into the interior of the fireplace, the purpose of the whole arrangement being to confine the combustion process substantially to the fireplace zone.

Several embodiments of the invention are illustrated by way of example in the a accompanying drawings in which:

FIG. 1 shows a longitudinal section through a shaft furnace with horizontal air supply, horizontal collector flue, lateral cleaning doors, air dampers, and grates, taken along line lllIlI in FIG. 2;

FIG. 2 shows a cross-section of the shaft furnace according to FIG. 1, taken along line II in FIG. 1;

FIG. 3 shows a cross section of the shaft furnace according to FIG. 1 of the cornered type, with the cover removed, taken along the line "-11 of FIG. 1;

FIG. 4 shows a cross-section of the shaft furnace according to FIG. 1, of the circular type, with the cover removed taken along the line lV-IV of FIG. 2;

FIG. 5 shows a longitudinal section through a shaft furnace with horizontal air supply and standing flues, taken along line VI-VI of FIG. 6;

FIG. 6 shows a cross-section of the shaft furnace according to FIG. 5, along line V-V of FIG. 5.

The shaft furnace for the combustion of wood and refuse shown in FIGS. 1 to 4 presents a shaft 1. This may have a polygonals, in particular, a four-cornered, cross-section (FIG. 3) or a round cross-section (FIG. 4). The shaft, normally vertical, may have a slant in parts. Arranged above the bottom 3 and opposite each other are two ash doors 5 with air dampers 7 and bar grates 9. The shaft can be closed by a hinged cover 11, which is opened for the normal charging of the furnace. For inspection purposes and partial charges, the cover is provided with an aperture which can be closed by a door 13 on a neck 15. Extending above the bottom 3 and parallel thereto across the whole furnace width is a self-contained fireplace 17 which forms a unit both functionally and structurally, and above it is a second fireplace 19 of slightly different design. The fireplace 17 comprises a water-bearing drum 21 with an outer jacket 22, a flue 24 arranged inside the drum 21, further flues 28 which extend through the drum 21 and connect the flue 24 with the furnace chamber 26, and still further flues 30 which extend inside the drum 21 and parallelt o the flue 24 and which communicate with the flue 24 through a return chamber 32. It is possible, in the versions shown in FIGS. 1 and 3, to connect an oil-firing system 34 at the inlet of the flue 24.

Fixed to the upper half of the drum 21 on both sides are grate plates 36 with air vents 38 which are supplied with combustion air through the air ducts 40 extending parallel to the drum 21. Each duct 40 is provided at one end with an air damper 48, at the other with a cleaning door 50. Owing to these air dampers, each air supply duct functions independently, thus making local firing possible in the shaft.

The ash doors 5 are also provided with air dampers 7 and grates 9. The combustion air entering here escapes likewise through the nearest flues 28.

The upper fireplace 19 comprises a trapezoidal duct 42 for channeling combustion air, which passes out upwards and sideways through vents 44 in the grate 46. The duct 42 is provided at one end with an air damper 48, while its other end is closed by a door 50, which can be opened for cleaning the duct 42. The upper portion of the shaft 1 is partitioned by partitions 52. These permit combustion of different types of fuel and also separate combustion of various types of charges.

The material to be burned is tipped into the shaft, open at the top, by tippers, loading shovels or the like, and the furnace can be filled to any degree desired. Then each fireplace is ignited separately. Owing to the structural unity of the fireplace, the whole furnace charge does not burn, but only that in the zone around the fireplace. The combustion air passing through the air vents 38 to the burning material in the chamber 26 maintains the combustion. The combustion gases escape through the flues 28 which happen to be nearest the vents 38, so that only firebeds of small dimensions can develop. The vents 38 on the upper horizontal grate surfaces of the plates 36, onwhich the fuel rests, are more numerous than those in the side walls. These latter vents are in particular designed for after-combustion and also the blowing-out of ash getting into the air ducts 40.

The simplified fireplace 19 is designed to interact with the main fireplace 17. The conical or trapezoidal cross-section of the grate 46 ensures that the gases pass out of the fireplace 19 into the nearest flues 28 of the fireplace 17.

The air dampers 7 and 48 permit a suitable air supply to be set. The gases entering the flues 28 meet in the collector flue 24, which they leave through the return chamber 32. They pass into the flues 30 and thence through the gas outlet into the chimney (not shown).

For very large furnaces, it is of course also possible to provide for several main fireplaces 17, in particular arranged side by side, with or without subsidiary fireplaces 19 (one or several to each main fireplace 17).

The water cooling the drum 21 can be used for heating purposes. As shown in FIGS. 1 to 4, the lower portion of the furnace is preferably cased with firebrick.

FIGS. 5 and 6 show an embodiment different from that shown in FIGS. 1 to 4. The walls 62 of the shaft 60 are made of fireproof material or may instead be watercooled. There are three fireplaces 64, 65 and 66, which can function independently of each other. The middle fireplace 64 presents two lateral angled grate plates 70 which are provided with air vents 68 and which, in conjunction with the lower ends 72 of shaft walls 74, delimit the position of air ducts 76. The ends 72 concurrently form a flue hood, from which the flues 77 lead into flue boxes 78. From these, the gases pass through gas outlets 79 into the chimney (not shown). The two lateral fireplaces 65 and 66 have an analogous structure and function accordingly. Here again, the number of fireplaces depends on the cross-sectional dimension of the furnace.

The furnace claimed hereunder differs from the known systems in particular in that the combustion gases not only pass into lateral flues or flues arranged above the air supply points, but also escape through flues arranged below the air supply points.

Due to the fact that flues are also arranged below the air supply points, the length of the flame path is independent of the shaft diameter. The gases need not permeate and ignite large quantities of fuel before reaching the nearest flue.

Each fireplace has an air supply with an associated flue. Thus, firing can be controlled individually for each fireplace by regulating the air supply, and this presents an advantage especially with varying heat requirements. 7

The air supply ducts may extend through the combustion chamber horizontally, side by side or in stairway fashion. Whatever the arrangement is, the length of flame path is preferably set in such a way that part of the combustion air escapes through the flue located below the air supply duct, while part escapes through the nearest flue. Each flue thus receives the gases from two different air supply ducts. This mixing of the gases results in better combustion.

In the embodiments illustrated in FIGS. 1 to 6, all flues lead into a common collector flue for further combustion of the gases.

It will be obvious to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is shown in the drawings and described in the specification. What is claimed is:

l. A shaft furnace for the combustion of wood waste and refuse comprising:

a housing; and

a fireplace means connected to said housing therewithin and surrounded by the material to be burned, for burning the material in the immediate vicinity thereof;

said fireplace means comprising air supply means for supplying the oxygen required for combustion;

at least one grate, having air vents therein, associated with said air supply means for allowing said oxygen to pass therethrough and come into contact with the material to be burned, and

flue means within said fireplace means and at least partially below the level of said grate for carrying the combustion gases from the vicinity of said grate into the interior of said fireplace means and thence out of the furnace thus confining the combustion process substantially to the zone of said fireplace means.

2. A shaft furnace according to claim 1, wherein in addition to the said fireplace means at least one subsidiary fireplace is connected to said housing therewithin above said fireplace means.

3. A shaft furnace according to claim 2, wherein said fireplace means and said fireplace extend through the walls of said housing and are provided outside with cleaning doors and air dampers.

4. A shaft furnace according to claim .1, further including partitions for subdividing the interior of said housing.

5. A shaft furnace according to claim 1 wherein said flue means comprises a plurality of ducts, none of which are above the level of said air vents such that the combustion gases flow downwardly into said flues.

6. A shaft furnace according to claim 1 wherein said grate has an angular cross-section, the interior of said grate serving as an air duct, said air vents being provided along the entire length of said grate.

7. A shaft furnace according to claim 6 wherein said flue means comprises a horizontal flue hood having access flues therethrough and said grates are connected to the exterior of said flue hood. v

8. A shaft furnace according to claim 6 wherein said flue means comprises a vertical flue hood having an access opening therebeneath and said grate is connected to the exterior of said hood.

9. A shaft furnace according to claim 8 further including a plurality of said grates and a plurality of said flue hoods and wherein said grates are offset from one another in a stairway fashion.

10. A shaft furnace according to claim 1, wherein said fireplace means further includes a water-cooled drum; wherein said flue means comprises a longitudinal flue mounted within said drum, access flues extending from said longitudinal flue to the exterior of said drum, and continuation flues in flow continuation with said longitudinal flue and leadingout ofthe furnace; and further wherein said grate is attached to said drum such that an air duct is formed between said drum and said grate.

11. In a shaft furnace comprising at least one supporting structure within the material to be burned, a flue duct having flue duct openings within said supporting structure and with at least one fixed grate having air supply ducts, the improvement wherein each of said grates (36 or is mounted on said supportingstructure (21, 74) that contains said flue ducts (24, 77), and the flue duct openings (28) are in close proximity to said air supply ducts (38 and 68).

12. A shaft furnace in accordance with claim 11, wherein said supporting structure (21) is made in the form of a drum, from which said grates (36) project laterally.

13. A shaft furnace in accordance with claim 12, wherein said drum-shaped supporting structure (21) has a central flue-gas collecting duct (24) with radial ducts which lead to said flue-gas duct openings on th circumference of said drum.

14. A shaft furnace in accordance with claim 12, wherein at least a portion of said flue-gas duct openings (28) are located beneath said grate (36).

15. A shaft furnace in accordance with claim 11 wherein additional auxiliary grates (9,19) with air supply ducts are mounted opposite said flue-gas duct openings (28).

16. A shaft furnace in accordance with claim 11, wherein the supporting structure (74) equipped with said flue gas duct openings consists of a vertical fluegas shaft, said shaft having at its lower end at least one laterally projecting grate (70).

17. A shaft furnace in accordance with claim l6; 

1. A shaft furnace for the combustion of wood waste and refuse comprising: a housing; and a fireplace means connected to said housing therewithin and surrounded by the material to be burned, for burning the material in the immediate vicinity thereof; said fireplace means comprising air supply means for supplying the oxygen required for combustion; at least one grate, having air vents therein, associated with said air supply means for allowing said oxygen to pass therethrough and come into contact with the material to be burned, and flue means within said fireplace means and at least partially below the level of said grate for carrying the combustion gases from the vicinity of said grate into the interior of said fireplace means and thence out of the furnace thus confining the combustion process substantially to the zone of said fireplace means.
 2. A shaft furnace according to claim 1, wherein in addition to the said fireplace means at least one subsidiary fireplace is connected to said housing therewithin above said fireplace means.
 3. A shaft furnace according to claim 2, wherein said fireplace means and said fireplace extend through the walls of said housing and are provided outside with cleaning doors and air dampers.
 4. A shaft furnace according to claim 1, further including partitions for subdividing the interior of said housing.
 5. A shaft furnace according to claim 1 wherein said flue means comprises a plurality of ducts, none of which are above the level of said air vents such that the combustion gases flow downwardly into said flues.
 6. A shaft furnace accOrding to claim 1 wherein said grate has an angular cross-section, the interior of said grate serving as an air duct, said air vents being provided along the entire length of said grate.
 7. A shaft furnace according to claim 6 wherein said flue means comprises a horizontal flue hood having access flues therethrough and said grates are connected to the exterior of said flue hood.
 8. A shaft furnace according to claim 6 wherein said flue means comprises a vertical flue hood having an access opening therebeneath and said grate is connected to the exterior of said hood.
 9. A shaft furnace according to claim 8 further including a plurality of said grates and a plurality of said flue hoods and wherein said grates are offset from one another in a stairway fashion.
 10. A shaft furnace according to claim 1, wherein said fireplace means further includes a water-cooled drum; wherein said flue means comprises a longitudinal flue mounted within said drum, access flues extending from said longitudinal flue to the exterior of said drum, and continuation flues in flow continuation with said longitudinal flue and leading out of the furnace; and further wherein said grate is attached to said drum such that an air duct is formed between said drum and said grate.
 11. In a shaft furnace comprising at least one supporting structure within the material to be burned, a flue duct having flue duct openings within said supporting structure and with at least one fixed grate having air supply ducts, the improvement wherein each of said grates (36 or 70) is mounted on said supporting structure (21, 74) that contains said flue ducts (24, 77), and the flue duct openings (28) are in close proximity to said air supply ducts (38 and 68).
 12. A shaft furnace in accordance with claim 11, wherein said supporting structure (21) is made in the form of a drum, from which said grates (36) project laterally.
 13. A shaft furnace in accordance with claim 12, wherein said drum-shaped supporting structure (21) has a central flue-gas collecting duct (24) with radial ducts which lead to said flue-gas duct openings on the circumference of said drum.
 14. A shaft furnace in accordance with claim 12, wherein at least a portion of said flue-gas duct openings (28) are located beneath said grate (36).
 15. A shaft furnace in accordance with claim 11 wherein additional auxiliary grates (9,19) with air supply ducts are mounted opposite said flue-gas duct openings (28).
 16. A shaft furnace in accordance with claim 11, wherein the supporting structure (74) equipped with said flue gas duct openings consists of a vertical flue-gas shaft, said shaft having at its lower end at least one laterally projecting grate (70).
 17. A shaft furnace in accordance with claim 16, wherein said flue-gas duct openings are located beneath said grate (70).
 18. A shaft furnace in accordance with claim 11, wherein several identical supporting structures with flue-gas ducts and grates are mounted in parallel in the shaft furnace.
 19. A shaft furnace according to claim 1 wherein said flue means is entirely below the level of said grate, and wherein said grate is positioned substantially directly above said flue means so that no material to be burned can enter and clog the entrances of said flue means. 